Advanced Micro Devices Corporation

Hewlett-packard Development Company, L.p.

Other

Ati Technologies Ulc

Paul J Moyer

William Louie Walker

Jay E Fleischman

Douglas Benson Hunt

John Kelley

Eric Christopher Morton

John Kalamatianos

Jagadish B Kotra

Marius Evers

Richard Martin Born

Gabriel H Loh

Michael T Clark

Bryan P Broussard

Kai Troester

Philip Ng

Vydhyanathan Kalyanasundharam

David S Christie

David A Kaplan

Joseph Lee Greathouse

Tarun Nakra

Paul C Miranda

Patrick J Shyvers

Elizabeth Morrow Cooper

Akhil Arunkumar

Pravesh Gupta

Sriram Srinivasan

Scott Thomas Bingham

Christopher Todd Weller

Richard H Lee

Ciji Isen

Vanchinathan Venkataramani

Nicholas Dean Lance

Cache replacement policies are described. In accordance with the described techniques, a request for data is received and a cache replacement policy controls how a controller responds to the request. The cache replacement policy assigns each cacheline a priority value, which indicates whether the cacheline should be preserved relative to other cachelines, in response to the request being a cache miss that necessitates eviction of at least one cacheline. The cache replacement policy decrements priority values until at least one cacheline achieves a minimum priority value, at which point a cacheline is evicted. The cache replacement policy designates certain cachelines as protected, either via a separate protected indicator or via the cacheline's priority value, which causes unprotected cachelines to be selected for eviction while favoring preservation of protected cachelines in the cache.

Super-temporal cache replacement policy

An entry of a last level cache shadow tag array to track pending last level cache misses to private data in a previous level cache (e.g., an L2 cache), that also are misses to an exclusive last level cache (e.g., an L3 cache) and to the last level cache shadow tag array. Accordingly, last level cache miss status holding registers need not be expended to track cache misses to private data that are already being tracked by a previous level cache miss status holding register. Additionally or alternatively, up to a threshold number of last level cache pending misses to the same shared data from different processor cores are tracked in the last level cache shadow tag array, and any additional last level cache pending misses are tracked in a last level cache miss status holding register.

Method and apparatus for increasing memory level parallelism by reducing miss status holding register allocation in caches

In response to generating one or more speculative prefetch requests for a last-level cache, a processor determines prefetch analytics for the generated speculative prefetch requests and compares the determined prefetch analytics of the speculative prefetch requests to selection thresholds. In response to a speculative prefetch request meeting or exceeding a selection threshold, the processor selects the speculative prefetch request for issuance to a memory-side cache controller. When one or more system conditions meet one or more condition thresholds, the processor issues the selected speculative prefetch request to the memory-side cache controller. The memory-side cache controller then retrieves the data indicated in the selected speculative prefetch request from a memory and stores it in a memory-side cache in the data fabric coupled to the last-level cache.

Selective speculative prefetch requests for a last-level cache

Systems, apparatuses, and methods for employing system probe filter aware last level cache insertion bypassing policies are disclosed. A system includes a plurality of processing nodes, a probe filter, and a shared cache. The probe filter monitors a rate of recall probes that are generated, and if the rate is greater than a first threshold, then the system initiates a cache partitioning and monitoring phase for the shared cache. Accordingly, the cache is partitioned into two portions. If the hit rate of a first portion is greater than a second threshold, then a second portion will have a non-bypass insertion policy since the cache is relatively useful in this scenario. However, if the hit rate of the first portion is less than or equal to the second threshold, then the second portion will have a bypass insertion policy since the cache is less useful in this case.

System probe aware last level cache insertion bypassing

Disclosed is a system and method for use in a cache for suppressing modification of cache line. The system and method includes a processor and a memory operating cooperatively with a cache controller. The memory includes a coherence directory stored within a cache created to track at least one cache line in the cache via the cache controller. The processor instructs a cache controller to store a first data in a cache line in the cache. The cache controller tags the cache line based on the first data. The processor instructs the cache controller to store a second data in the cache line in the cache causing eviction of the first data from the cache line. The processor compares based on the tagging the first data and the second data and suppresses modification of the cache line based on the comparing of the first data and the second data.

Suppressing cache line modification

Processor-guided execution of offloaded instructions using fixed function operations is disclosed. Instructions designated for remote execution by a target device are received by a processor. Each instruction includes, as an operand, a target register in the target device. The target register may be an architected virtual register. For each of the plurality of instructions, the processor transmits an offload request in the order that the instructions are received. The offload request includes the instruction designated for remote execution. The target device may be, for example, a processing-in-memory device or an accelerator coupled to a memory.

Processor-guided execution of offloaded instructions using fixed function operations

Systems and methods for cache replacement are disclosed. Techniques are described that determine a re-reference interval prediction (RRIP) value of respective data blocks in a cache, where an RRIP value represents a likelihood that a respective data block will be re-used within a time interval. Upon an access, by a processor, to a data segment in a memory, if the data segment is not stored in the cache, a data block in the cache to be replaced by the data segment is selected, utilizing a binary tree that tracks recency of data blocks in the cache.

Re-reference interval prediction (RRIP) with pseudo-LRU supplemental age information

Systems, apparatuses, and methods for arbitrating threads in a computing system are disclosed. A computing system includes a processor with multiple cores, each capable of simultaneously processing instructions of multiple threads. When a thread throttling unit receives an indication that a shared cache has resource contention, the throttling unit sets a threshold number of cache misses for the cache. If the number of cache misses exceeds this threshold, then the throttling unit notifies a particular upstream computation unit to throttle the processing of instructions for the thread. After a time period elapses, if the cache continues to exceed the threshold, then the throttling unit notifies the upstream computation unit to more restrictively throttle the thread by performing one or more of reducing the selection rate and increasing the time period. Otherwise, the unit notifies the upstream computation unit to less restrictively throttle the thread.

Throttling while managing upstream resources

A cache stores, along with data that is being transferred from a higher level cache to a lower level cache, information indicating the higher level cache location from which the data was transferred. Upon receiving a request for data that is stored at the location in the higher level cache, a cache controller stores the higher level cache location information in a status tag of the data. The cache controller then transfers the data with the status tag indicating the higher level cache location to a lower level cache. When the data is subsequently updated or evicted from the lower level cache, the cache controller reads the status tag location information and transfers the data back to the location in the higher level cache from which it was originally transferred.

System and method for storing cache location information for cache entry transfer

Techniques for invalidating cache lines are provided. The techniques include issuing, to a first level of a memory hierarchy, a weak exclusive read request for a speculatively executing store instruction; determining whether to invalidate one or more cache lines associated with the store instruction in one or more memories; and issuing the weak invalidation request to additional levels of the memory hierarchy.

Weak cache line invalidation requests for speculatively executing instructions

A computing system may implement a split random number generator that may use a random number generator to generate and store seed values in a memory for retrieval and use by one or more core processors to generate random numbers for secure processes within each core processor.

Split random number generator

A processor includes a cache having two or more test regions and a larger non-test region. The processor further includes a cache controller that applies different cache replacement policies to the different test regions of the cache, and a performance monitor that measures performance metrics for the different test regions, such as a cache hit rate at each test region. Based on the performance metrics, the cache controller selects a cache replacement policy for the non-test region, such as selecting the replacement policy associated with the test region having the better performance metrics among the different test regions. The processor deskews the memory access measurements in response to a difference in the amount of accesses to the different test regions exceeding a threshold.

Cache access measurement deskew

Techniques for performing cache operations are provided. The techniques include tracking performance events for a plurality of test sets of a cache, detecting a replacement policy change trigger event associated with a test set of the plurality of test sets, and in response to the replacement policy change trigger event, operating non-test sets of the cache according to a replacement policy associated with the test set.

Growing community of inventors

Fort Collins, CO, United States of America

Paul J Moyer